The present invention relates to an electrical power supply apparatus that is supplied with radiant energy, in particular, a photovoltaic electrical power supply apparatus, and a method for operating an electrical power supply apparatus of this type.
Electrical power supply apparatuses that are supplied with radiant energy have the disadvantage that they can only produce electrical power when there is sufficient radiation (e.g., sunlight) striking the electrical power supply apparatus. As a result, electrical or mechanical power is generally available from electrical power supply apparatuses of this type only during the day, whereas no electrical or mechanical power can be produced at night. These known electrical power supply apparatuses are thus not suitable for applications in which electrical or mechanical power needs to be provided around the clock at sites far away from any other sources of electrical power.
Exemplary embodiments of the present invention are directed to an electrical power supply apparatus that is supplied with radiant energy, which apparatus is capable of providing electrical or mechanical power around the clock.
The electrical power supply apparatus according to the invention is equipped with at least one electrical generator converting radiant energy into electrical power, in particular, a photovoltaic solar generator that converts the impinging radiant energy into electrical power; with at least one hydrogen generator to produce hydrogen from water; with at least one water reservoir that is connected through a first water line to the hydrogen generator; with at least one hydrogen reservoir that is connected through a first hydrogen line to the hydrogen generator; with at least one fuel cell or at least one hydrogen combustion engine, which fuel cell or engine is connected through a second hydrogen line to the hydrogen reservoir and is connected through a second water line to the water reservoir, and with a control unit that is electrically connected to the electrical power generator, the hydrogen generator, and the fuel cell or hydrogen engine. To produce electrical power, the hydrogen combustion engine can also be connected to a second electrical power generator associated with this engine, which generator can also be controlled by the control unit. To produce mechanical power, an electric motor supplied with electrical power from the fuel cell can also be provided, which motor can also be controlled by the control unit.
The parallel provision according to the invention of, for example, a photovoltaic solar generator, a hydrogen generator, and a fuel cell enables a portion of the electrical power produced by the solar generator during the day, when sufficient radiant solar energy is available, to be used to produce hydrogen from water, the hydrogen then being recombined in the fuel cell with atmospheric oxygen to form water so as to enable the fuel cell to produce electrical power either at night when radiant solar energy is not available, or whenever radiant solar energy is not available in sufficient amounts. As a result, electrical power is available continuously that can be supplied directly by the solar generator, or indirectly through the fuel cell. The only input energy for this inventive system is the radiant solar energy, since water, hydrogen and oxygen form a closed loop that includes reservoirs for water and for hydrogen.
The power supply apparatus according to the invention is not restricted to radiant solar energy, but instead can be applied wherever an electrical power generator can produce electrical power from a source of radiant energy that does not radiate continuously and wherever an uninterrupted supply of electrical power must be ensured.
In a preferred development, the hydrogen generator includes a water electrolysis unit.
The electrical power generator that is preferably in the form of a solar generator includes at least one support element provided with solar cells, the support element being composed of a panel.
Alternatively, the support element can be composed of a thin film, preferably a polyester film, and furthermore preferably composed of a biaxially oriented polyester film. This structure provides a very low weight for the support element, which exhibits very high strength with low weight—in particular if the element is composed of a biaxially oriented polyester film such as that known, for example, under the trade name “MYLAR.”
An especially preferred approach is for the solar cells to be thin-film solar cells, where preferably cadmium-telluride cells in particular are used. Thin-film solar cells also feature very low weight, with the result that in combination with the support element composed of a thin film they provide a very light solar generator.
The electrical power supply apparatus is preferably equipped additionally with an electrical storage means, that can be provided, for example, as a battery. This electrical power storage means forms a buffer storage means that can deliver electrical power on a short-term basis whenever the electrical power generator is not being supplied with sufficient radiant energy for a short period of time. This energy storage means thus functions to bridge the time that is required to activate the fuel cell, or if the fuel cells have not been activated, thereby bridging that time period which is required, for example, during short-term obscuration of sunlight until the sunlight again impinges on the electrical power generator.
The photovoltaic electrical power supply apparatus according to the invention is preferably equipped with a control unit that is designed so that the electrical power produced by the electrical power generator is supplied to a consumer terminal of the electrical power supply apparatus whenever radiant energy is present, and so that this device activates the fuel cell to deliver electrical power to the consumer terminal whenever radiant energy is not available or whenever the electrical power produced by the electrical power generator is not sufficient to meet the specified power requirement. This control unit can ensure that the fuel cell is activated automatically whenever insufficient radiant energy or no radiant energy is available.
That embodiment of the control unit is especially preferred whereby it delivers a portion of the electrical power produced by the electrical power generator to the hydrogen generator when solar radiant energy, in particular, is present, and whereby the device feeds water from the water reservoir to the hydrogen generator such that the hydrogen generator is activated so as to produce hydrogen from the water supplied to it, the hydrogen being stored in the hydrogen reservoir. In this embodiment, a portion of the electrical power produced by the electrical power generator is used to operate the hydrogen generator to produce hydrogen, which is required by the fuel cell to produce electrical power whenever the electrical power generator is supplying no electrical power or insufficient electrical power. The control unit here can control the amount of electrical power that is supplied to the hydrogen generator, or also to control the operating times for the hydrogen generator as a function of the available supply of hydrogen.
It is also advantageous if a portion of the electrical power produced by the electrical power generator and/or by the fuel cell is supplied to the energy storage means in order to charge this energy storage means. This ensures that electrical power is continuously being buffered in the energy storage means, which power can be retrieved directly therefrom when needed.
In a preferred embodiment of the electrical power supply apparatus according to the invention, which embodiment is suitable for applications in vehicles or in aircraft with restricted weight requirements but where sufficient space is available, the hydrogen is stored as a gas in an equalized-pressure balloon or in a very light pressurized tank that is implemented in a manner analogous to a non-rigid airship, which container produces a significant lift force due to the low density of the hydrogen gas, instead of adding weight as in the case with other types of energy storage means (for example, batteries or pressurized gas cylinders).
The present invention is also directed to a method for operating the photovoltaic electrical power supply apparatus.
To this end, a portion of the electrical power produced by the electrical power generator is continuously supplied to the hydrogen generator, whereupon the hydrogen generator separates out the hydrogen from the water supplied from the water reservoir, the hydrogen being stored in the hydrogen reservoir, and the fuel cell produces electrical power from the hydrogen supplied to it from the hydrogen reservoir whenever radiant energy is absent or insufficient radiant energy is provided. If requirements specify a high power-to-weight ratio, a hydrogen combustion engine produces electrical power from the hydrogen supplied from the hydrogen reservoir, which hydrogen combustion engine is equipped with an exhaust-gas turbocharger and high-pressure hydrogen injection unit, and includes a downstream electrical power generator.
This method provides the ability to operate the electrical power supply apparatus continuously over an extended period so that it can supply electrical power around the clock.
The following discussion more thoroughly describes and explains exemplary embodiments of the invention, including further design details and additional advantages, with reference to the attached drawings.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.